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What is Top-Level Domain?

In the DNS hierarchy, a top-level domain (TLD) is directly connected to the root. In the FQDN the top-level domain is “com”. As a direct delegation of the root domain, the list of top-level domains is relatively short and controlled by the ICANN and IANA organizations.

The 1500 top-level domains can be grouped into 4 main families that have evolved over time:

  • Country code domains following the ISO 3166 codes like .ar for Argentina, .hu for Hungary or .sn for Senegal.
  • Generic domains (highest proportion of the domains) in which we find the historical domains like .com or .edu and geographical examples such as cities and brands. Some very specific domains are sponsored by organizations or firms
  • Infrastructure domain .arpa, mainly used for mapping IP addresses to names in reverse resolution operation
  • Test domains for private usage like .test, .example, .localhost or .invalid. To avoid confusion, these domains are not installed in the root zone